DE1900291A1 - Process for the manufacture of pneumatic tires - Google Patents

Description

DR. MÜLLER-BOREDIPL-ΙΝΘ. 6RALFS 19QQ291

DIPL.-PHYS. DR. MANITZ DIPL.-CHEM. DR. DEUFEL

PATENT LAWYERS

Munich, 2.1.1969 Bol / Lg - D 1004

OHE DUNIiOP COMPANY LIMIOJED Ryder Street, St. James's, London S.W.1./England

Process for the manufacture of pneumatic tires

The invention relates to a method of manufacturing pneumatic tires, and more particularly relates to manufacturing of large tires such as those used for ground moving vehicles.

In the manufacture of tires having a deep tread pattern have had difficulties encountered in the flow of the tread rubber into the deep pattern of the standard matrix. This causes the breaker or carcass layers or both have been deformed or warped or distorted from the smooth, regular ring casing shape, so that corrugations are formed in the carcass or inlayers,

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with the corrugations directed inwardly towards of the flow of rubber into the deep pattern of the die.

The object on which the invention is based is to create a method for producing a pneumatic tire, in which the aforementioned disadvantages are overcome or substantially reduced.

Characterizes a method of manufacturing a pneumatic tire according to the invention in that tread elements made of an unvulcanized rubber composition with a generally concave, arched radially inner and outer Surface are formed so that the outer surface has a shape or design that corresponds essentially to that which is to be given to the corresponding part of the tread of the finished tire, that the elements end-to-end, Step-by-step (in sections) on the radial the outer surface of a tire without a tread is applied in order to create a complete tread for it, and that the finished tire is molded and vulcanized,

The tread elements that are formed, for example can be made by cutting, modeling or preforming, at least part of one or more tread ribs, -blocks, cleats or the like and can have dimensions substantially the same as the or slightly smaller than the dimensions of the corresponding parts of the finished tire, the latter allows expansion and flow of the rubber during molding and vulcanization. The elements can also comprise part or all of the sub-pattern gum. The number of elements on the treadless Tires are applied, depend on the size of the tire to be produced and its tread pattern for example, up to sixteen may be required.

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Preferably is the radially innermost surface of each
Elements are provided with a plurality of longitudinal or transverse grooves or other channels so that air which may otherwise be trapped can escape between the smooth-surfaced treadless tire and element. Alternatively or additionally, the radially innermost surface of the element can be smooth and the radially outermost surface of the
Treadless tires, ie the surface of the carcass or that of a layer of the under-tread rubber or insert which has been applied to the carcass, may be provided with grooves or channels.

The elements may be provided with end surfaces so that when applied to the treadless tire, these
Surfaces extend substantially radially, ie are the adjoining surfaces of two adjacent elements
essentially parallel. In a preferred alternative embodiment of the method according to the invention
however, these surfaces can be inclined up to 40 ° in the radial direction, the angle being obtained by
Pressing or cutting to form a V-shaped groove at the junction between two elements. During molding and vulcanization, this groove gradually closes, and as the V-grooves narrow, the end faces meet and join together. This preferred embodiment of the method: not only allows expansion and flow, wel- | This takes place under pressure during vulcanization, but also reduces the likelihood that air will be trapped at the joints.

The invention further comprises a pneumatic tire of either radial or cross-ply construction either with textile or metallic

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Strengthening made according to the procedure described here became.

One embodiment of the invention is exemplified below in application in the manufacture of a tire for earthmoving machines with deep components based on the DrawingWBLWritten; in this sseigen:

Figure 1 is a flow diagram of the method according to the invention,

FIG. 2 shows a plan view of part of the tread of a ψ tire which, according to the method according to the invention

was made, and

Figure 3 is a partial sectional view along line A-A of Figure 2, in which an element is positioned on the treadless tire.

Part of the apparatus used in the inventive method described herein is essentially the same as described and disclosed in co-pending (British) patent application 3249/67 generally a segment-shaped tire molding unit and a conventional press for preforming the tread elements elements by filling the elements with rubber. In addition, common machines are provided for manufacturing or Forming and shaping the carcass, a dividing device or switching machine by means of which the tread elements the tread-free tires are applied and a table on which the pre-formed tread elements are stored and transferred from the press to the dividing device or switching machine in a manner yet to be described Way.

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The molding unit generally has a discontinuous hing of segments that moves radially inward to form a continuous ring around a vulcanized tire that is coaxial is arranged within the Hinges. The segments are each with a part on their radially inner surfaces of the complete die forming the tread, and it is this part of the tread which is preformed or formed by a segment which in this embodiment is referred to as the "tread element" will.

As shown in Figures 2 and 3, the Tread elements 1 in this embodiment each have two curved traction pieces or traction bars 2 which, when placed on a treadless tire 3, differ from the central equatorial Area of the tire crown (crown) each extend one or one to each shoulder 4 of the tire. To the For the manufacture of the elements, the tread rubber is mixed in a mill and cut into pieces (blanks) (Figure 1 stage f), which are heated in an oven (stage g) before molding in a press (stage h) of known type. This press has a lower pressure piece on which a segment, which is similar to one of those which are provided in the mold unit is arranged in an inverted position and an upper one Pressure piece for supporting an arcuate pressing tool in order to press the blank into the preform segment and to form a generally concave arcuate radially inner surface having a plurality of relatively narrow or small grooves are provided which extend transversely with respect to the finished tire. the arcuate area has a slightly larger one

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Radius of curvature than that of the radially outer surface of a Layer of the under-tread gmnmi a, which is formed on the Tire carcass is arranged, the curvature being viewed in a plane which contains the carcass axis. The fact that both the element and the rubber layer have curved surfaces facilitates the arrangement of the element in its position, while the slightly larger curvature and the grooves allow the air to escape between the element and the layer, as will be apparent from the description below;

After preforming, the elements are placed on a suitable * nicely shaped table stored where it is in essentially their preformed shape and shape are stored and held until needed.

A carcass for the tire is made in a conventional manner on a molding machine (Figure 1, Stage a) and is shaped by a membrane in substantially its final U-shaped cross-sectional shape and Diameter (step b).

A ply construction or reinforcement strip construction is applied to the radially outer surface of the molded carcass and a single rubber layer is applied radially outward on the reinforcement insert. This treadless Tire is then removed from the molding apparatus and a vulcanizing bag or tube is inserted (Stage c) and then attaching tabs or tab rings (stage d), one ring to each Bead.

In order to obtain an exact arrangement of the tread elements in In relation to the molding die in the molding unit.

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ORfGfNAL INSPECTED

perform, it is necessary. " the tread elements on the treadless tire on a sub-machine or Apply switching device (stage e). For this reason, the bead clip rings are provided with a keyway, which coincides in its position with a wedge on a central protrusion, which is on the central support of the part or indexing machine is arranged to support the treadless tire coaxially therewith. The tread elements are from the table where they were stored and one is currently placed in a jig (see Fig. 3). Suction is created around the Element (which is shown in phantom outlines in Figs. 2 and 3) to be held in the jig while the element is applied to the circumference of the treadless tire 3 by means of a hydraulic jar or piston-cylinder device. When the element is in place, suction is applied lifted, the clamping device removed and the treadless tire switched to a partial position, ready to take the next item. Sa each element has a larger radius of curvature (viewed in a plane, which contains the carcass axis) than the treadless tire touches the central apex area of the treadless tire The element tires first and air which might otherwise be trapped is axially outward pressed, this removal is additionally facilitated by the not shown grooves, which on the element 1 are provided. This arrangement and procedure ensure that the elements are accurate and correct with respect to the clamp rings or tire rings and the valves of the vulcanizing bag are arranged so that when the finished formed, unvulkani-based tires are arranged in the mold unit, the elements also accurately and correctly in relation to each other are arranged on the molding die.

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After assembly, the tire is placed in the molding unit Inserted, the vulcanizing hose, is slightly pressurized to keep the tire moving forward against it to support moving segments, and the segments are moved radially inward (Fig. 1, stage i). In the end the tire and mold assembly is inserted into a vulcanizing unit to vulcanize the tire under pressure, with which the vulcanizing hose is applied (stage j).

Since the elements are each provided with end faces 6 in the preform stage, which when the element is on the The treadless tire is arranged to extend at an angle of 20 ° to the radial direction a V-shaped groove 7 formed at the junction between two elements by their juxtaposed. End faces. Some amount of rubber flow and expansion takes place during the molding step and the Elements gradually join together or gradually stick together as the V-grooves get smaller will. These inclined end faces not only allow the slight expansion and flow, but it also reduces the likelihood or possibility of air being trapped at the joints will.

In a modification of the embodiment just described, instead of each element of its segment removed after preforming and then stored, the element is transferred from the press to the treadless tire in its segment, on its outer surface applied and then removed the segment. The segment effectively replaces the jig referred to above.

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In the aforementioned embodiment and / or modification For example, the elements are preformed in a tread segment which is essentially the same as that shown in FIG the molding unit is used. Alternatively, the segments of the mold unit can be larger than that Preform segment, the larger segments being equivalent to a number of smaller preform segments. E.g. if 12 elements are provided, only three mold segments could be used in the mold unit, each of these segments is equivalent to four preform segments.

Although the preferred embodiment described above is a segmented one Form is used, it will be understood that a two-part form can be used in an alternative manner can be used, the selection depending largely on the tread pattern to be formed. However Difficulties can arise during, particularly when a two-part mold is used of closing the mold if the pattern of the tread, which is made up of elements, is exactly that of the molding die corresponds to or is adapted to, with a shift or offset of the tread rubber occurs, when the die comes into contact with the rubber. To overcome this difficulty are the dimensions of the elements designed to be slightly smaller than the corresponding dimensions of the die in order to achieve a To allow closure without displacement or displacement occurring, with the resulting gaps between the rubber and the die are filled during molding and vulcanization by a part of the under tread rubber, which is generally radial flows outwards through the general overall expansion, which takes place under the pressure with which the volcanic

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siersclilauch or -bag is applied and the minor Thermal expansion of the rubber.

An advantage of the method described above is that the useful life of the mold unit is considerably reduced with respect to that which is in the at the same time current (British) patent application 3249/67 of Applicant is described.

- patent claims -

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ORfGFNAL INSPECTED

Claims (18)

Patent claims 1. A method of making a pneumatic tire, thereby Marked e i c h η e t that tread elements made of a non-vulcanized rubber composition be formed with a generally arcuate radially inner and outer surface that the outer Surface has a shape which substantially corresponds to that which is on the corresponding part of the tread of the fully formed tire is to be applied that the elements end-to-end step-by-step (in sections) on the radially outer surface of the treadless tire are applied to a to create a complete tread for this and that the complete tire is molded and vulcanized will. 2. The method according to claim 1, characterized in that that the treadless tire has a carcass. 3. The method according to claim 2, characterized in that that the treadless tire is a 909836/0846 ORIGINAL INSPECTED Has reinforcement insert (breaker), which on the carcass is applied. 4. The method according to claim 2 or 3, characterized g e characterizing t that the treadless heat is a layer of under tread rubber. 5. "The method according to any one of the preceding claims, characterized characterized that ^ each element at least _m . _ ■ at least ^ _, ..-, - .. “. . has part of a surface rib. 6. The method according to any one of claims 1 to 4, characterized in that k e hn indicates that each element has at least one Has part of at least one tread block or lug. 7. The method according to any one of the preceding claims, characterized characterized in that the elements when molded are, dimensions are substantially equal to the dimensions of the corresponding part of the tread of the fully formed tire. 8. The method according to any one of claims 1 to 6, characterized g ekenn ζ e i η e t that the elements, when molded, have dimensions that are slightly smaller than the dimensions of the corresponding parts of the tread of the fully formed tire to an extent and a Rubber flow during molding and vulcanization allow. . 9. The method according to any one of the preceding claims, characterized indicated that the elements comprise at least a portion of the sub-pattern rubber. 9098 3 6/0846 10. The method according to any one of the preceding claims, characterized in that the radial inner surface of each element is provided with several hats to allow air to escape, which "otherwise become trapped between the element and the treadless tire could. 11. The method according to any one of the preceding claims, characterized in that the radial outer surface of the treadless tire is grooved to prevent air from escaping which may otherwise become trapped between the element and the treadless tire could. 12. The method according to any one of the preceding claims, characterized in that the elements are provided with end faces which are essentially extend radially from the treadless tire when the elements are applied thereto. 13. The method according to any one of claims 1 to 11, characterized in that the elements have end faces which, when the elements are applied to the carcass, are inclined up to 40 ° in a radial direction of the treadless tire, and that a V-groove is thereby formed " between adjacent elements on the treadless tire. 14. The method according to any one of the preceding claims, characterized in that the elements 909836/0846 stored after molding so that they substantially retain their molded shape until they are Applying to the treadless soaps will be needed. 15- method according to one of the preceding claims, characterized in that the elements are held in a clamping device by means of suction while they are being applied to the treadless tire and that the suction is canceled when the element is in place. 16. The method according to any one of claims 1 to 14, characterized in that each element is preformed in a Lormsegment that the element, while it is still in its segment, on the running ^! faceless tire is transferred that the element ^! is applied to this and that, if the The element is in position on the treadless tire as the segment is removed from the element. 17 · Procedure as described in particular with reference to the drawing. 18. Pneumatic tire manufactured by the method according to one of the preceding Claims is made. 909836/0846 Lee rse it e